Hamilton City Council is trying to renew a bylaw that may be illegal - a ban on street prostitution that threatens a $20,000 fine.

The Prostitutes Collective (NZPC) is dead against it, and even the council admits it's on shaky legal ground. But Hamilton streets are now out of bounds for sex workers, and the council wants to keep it that way

"This bylaw is about the users, the public, the industry, and the perception of the city Hamilton," said Hamilton Mayor Andrew King.

Hamilton City Council unanimously voted last month to renew a 10-year-old bylaw which bans soliciting for sex on the street - a topic unfamiliar for some councillors.